The proposed research will seek to delve into the causal nexus influencing social organization and social behavior in fishes. A series of studies begun during the term of the present grant will be concluded, and several new studies will be initiated. Proposed research ranges from investigation of physiological mechanisms (C.N.S. ablation and corticosteroid assay) through experimental manipulation of spatial, trophic, temporal, configurational, and social parameters of group life in restricted environments, to combined field and laboratory study of territoriality in reef-inhabiting damsel fish. A variety of experimental and field techniques are being and will be used to reveal the nature of several proximate causes of social behavior and organization. By evaluating the results of these specific studies, we hope to shed light on the nature of ultimate causes of social order in teleost fishes, and in so doing provide information useful in phylogenetic analyses of vertebrate sociality.